EP2558518A1 - Composition thermoplastique formée à partir d'acide polylactique et d'un copolymère greffé élastomère - Google Patents

Composition thermoplastique formée à partir d'acide polylactique et d'un copolymère greffé élastomère

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Publication number
EP2558518A1
EP2558518A1 EP11769186A EP11769186A EP2558518A1 EP 2558518 A1 EP2558518 A1 EP 2558518A1 EP 11769186 A EP11769186 A EP 11769186A EP 11769186 A EP11769186 A EP 11769186A EP 2558518 A1 EP2558518 A1 EP 2558518A1
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EP
European Patent Office
Prior art keywords
graft copolymer
backbone
lactic acid
composition
thermoplastic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP11769186A
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German (de)
English (en)
Inventor
Chaobin He
Ting Ting Lin
Pui Kwan Wong
Suming Ye
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Agency for Science Technology and Research Singapore
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Agency for Science Technology and Research Singapore
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Publication date
Application filed by Agency for Science Technology and Research Singapore filed Critical Agency for Science Technology and Research Singapore
Publication of EP2558518A1 publication Critical patent/EP2558518A1/fr
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
    • C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
    • C08G63/08—Lactones or lactides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/005—Processes for mixing polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
    • C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2300/00—Characterised by the use of unspecified polymers
    • C08J2300/22—Thermoplastic resins
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones

Definitions

  • the present invention relates generally to thermoplastic
  • compositions and particularly to compositions formed from polylactic acid and an elastomer, and methods of forming such thermoplastic compositions.
  • thermoplastics are widely used. Many thermoplastic polymers, such as polystyrene and poly(methyl methacrylate), are brittle (i.e. easy to break) at low temperatures, which limits their applications. Polystyrene and poly(methyl methacrylate) may be "toughened” (i.e. made able to withstand greater strain without tearing or breaking) by adding an elastomeric copolymer during the manufacturing process, so that the elastomeric copolymer chains form dispersed rubber particles in the plastic matrix formed by the thermoplastic polymer. The resulting composition is still thermoplastic but can withstand higher stress and strain without breaking, as the presence of rubber particles can increase the energy required for crack propagation by causing cavitation, crazing, or shear banding.
  • thermoplastic materials with reduced brittleness. It is also desirable to provide alternative techniques to reduce brittleness of thermoplastic materials.
  • a composition comprising a thermoplastic polymer comprising a first enantiomer of lactic acid, and a graft copolymer comprising an elastomeric backbone and a side chain grafted to the backbone.
  • the side chain comprises a second enantiomer of lactic acid.
  • the first and second enantiomers have opposite chiral configurations.
  • the graft copolymer is selected and linked to the thermoplastic polymer by the first and second enantiomers of lactic acid so that the composition is thermoplastic and less brittle than the thermoplastic polymer.
  • composition comprising a thermoplastic polymer comprising a first enantiomer of lactic acid, and a graft copolymer comprising an elastomeric backbone and a side chain grafted to the backbone.
  • the side chain comprises a second enantiomer of lactic acid.
  • the first and second enantiomers have opposite chiral configurations.
  • the first and second enantiomers form a stereocomplex linking the thermoplastic polymer and the graft copolymer.
  • the thermoplastic polymer may comprise one of poly(L-lactic acid) and poly(D-lactic acid), and the side chain in the graft copolymer may comprise the other of poly(L-lactic acid) and poly(D-lactic acid).
  • the backbone of the graft copolymer may comprise a polyacrylate, such as poly(alkyl acrylate).
  • the poly(alkyl acrylate) may comprise n-butyl acrylate, n-hexyl acrylate, or n-octyl acrylate.
  • the side chain may be grafted to the backbone of the graft copolymer through a hydroxy- or amine- functionalized acrylate group.
  • the hydroxy-fuhctionalized acrylate group may comprise hydroxyethyl acrylate, such as 2-hydroxyethyl acrylate (HEA) or 2-hydroxyethyl methacrylate.
  • the composition may comprise about 1 to about 20 wt% of the graft copolymer.
  • the thermoplastic polymer may have a number average mojecular weight (Mn) of about 20,000 to about 500,000 g/mol
  • the elastomeric backbone of the graft copolymer may have an Mn of about 50,000 to about 500,000 g/mol
  • the side chain of the graft copolymer may have an Mn of about 2,000 to about 50,000 g/mol.
  • thermoplastic polymer may comprise 100 to 5000 repeating units of the first enantiomer of lactic acid.
  • the composition may have a percentage of elongation at break of about 23% to about 30%.
  • ln_anather_asp&ct,J:he ⁇ exemplary composition described herein.
  • the method comprises melting a first precursor for the thermoplastic polymer; melting a second precursor for the graft copolymer; and mixing the first and second precursors in a mixture at a
  • thermoplastic polymer above melting temperatures of the thermoplastic polymer and the graft copolymer to allow formation of stereocomplexes of lactic acid.
  • the method may comprise copolymerizing a monomer for the backbone and acrylate-terminated polylactic acid of the second enantiomer to form the second precursor for the graft copolymer.
  • the second precursor for the graft copolymer may also be formed by providing a copolymer precursor for the backbone, and reacting a lactic acid with the copolymer precursor for the backbone to graft a side chain comprising an acrylate-terminated polylactic acid from the copolymer precursor for the backbone.
  • thermoplastic material comprising melting a first thermoplastic material comprising a polymer formed of a first enantiomer of lactic acid; melting a graft copolymer, the graft copolymer comprising an elastomeric backbone and a side chain grafted to the backbone, the side chain Comprising a second enantiomer of lactic acid; mixing the melted first thermoplastic material with the melted graft copolymer for a sufficient time to allow the first and second enantiomers of lactic acid to react and link the polymer in the first thermoplastic material to the graft copolymer, to form a second thermoplastic material; and solidifying the second thermoplastic material to form a thermoplastic material that is less brittle than the first thermoplastic material.
  • the first thermoplastic material may comprise one of poly(L-lactic acid) and poly(D-lactic acid), and the side chain of the graft copolymer may comprise the other of poly(L-lactic acid) and poly(D-lactic acid).
  • the backbone of the graft copolymer may comprise a poly(alkyl acrylate), such as poly(n-butyl acrylate).
  • FIG. 1 is a schematic diagram of a synthesis route for forming a composition exemplary of an embodiment of the present invention.
  • FIG. 2 is a schematic diagram of an alternative synthesis route for forming an intermediate compound shown in FIG. 1.
  • thermoplastic compositions formed from a thermoplastic polymer and an
  • thermoplastic polymer includes an enantiomer of lactic acid.
  • graft copolymer includes a side chain having the opposite
  • the graft copolymer is selected and linked to the
  • thermoplastic polymer by the opposite enantiomers such that the brittleness of the thermoplastic composition is less than the brittleness of the thermoplastic polymer in its pure form.
  • Exemplary embodiments of the present invention also relate to thermoplastic compositions formed from a thermoplastic polymer of lactic acid and an elastomeric graft copolymer, which are linked by polylactic acid stereocomplexes (PLA stereocomplexes).
  • PLA stereocomplexes polylactic acid stereocomplexes
  • thermoplastic polymer includes a first enantiomer of lactic acid.
  • the thermoplastic polymer may be poly(L-lactic acid) (PLLA).
  • the thermoplastic polymer may be poly(D-lactic acid-)-(PDLA).
  • PLLA poly(L-lactic acid)
  • the thermoplastic polymer may be poly(D-lactic acid-)-(PDLA).
  • PDLA poly(D-lactic acid)-(PDLA).
  • L-lactic acid (LLA) and D-lactic acid (DLA) are enantiomers with opposite chiral configurations, and PLLA and PDLA can form a stereocomplex (PLA stereocomplex).
  • a PLA stereocomplex is different from a mere mixture of PLLA and PDLA in which no PLA stereocomplex is formed, in the sense that a PLA stereocomplex is a racemic configuration of PLLA and PDLA which exhibits properties that are significantly different from an optically pure PLA configuration.
  • the melting point temperature of a PLA material can be substantially increased due to formation of PLA stereocomplexes, as compared to the melting point temperature of a PLA material containing optically pure PLA configurations, or a mere mixture of PLLA and PDLA with no PLA stereocomplex.
  • the formation of PLA stereocomplex in a PLA-containing material dan be detected by measuring certain properties, such as melting point temperature, heat of fusion, and crystal structure (e.g. as characterized by resonance frequencies measured by a suitable spectroscopic technique) of the PLA-containing material.
  • melting point temperatures may be measured by differential scanning calorimetry (DSC)
  • heat of fusion may be measured by Dynamic
  • DMA Dynamic Microwave Analysis
  • crystal structures may be charaterized by X-ray spectroscopy.
  • Other suitable techniques may also be used to measure or charactorize the crystal structure in a material, as can be understood by those skilled in the art.
  • PLA stereocomplexes can form crystalline lattices.
  • the graft copolymer includes an elastomeric backbone and one or more side chains grafted to the backbone.
  • the backbone may be formed from any suitable elastomeric polymer as will be further described below.
  • the side chain includes a second enantiomer of lactic acid.
  • the first and second enantiomers have opposite chiral configurations.
  • the thermoplastic polymer comprises one of PLLA and PDLA
  • the side chains comprise the other of PLLA and PDLA.
  • the side chain of the graft copolymer may include PDLA when the thermoplastic polymer is PLLA; or may include PLLA when the thermoplastic polymer is PDLA.
  • At least some of the first and second enantiomers of polylactic acid in the composition form PLA stereocomplexes.
  • the backbone of the graft copolymer may be formed of a polyacrylate, such as poly(alkyl acrylate).
  • the monomer in the poly(alkyl acrylate) may include Ai-butyl acrylate, n-hexyl acrylate, or n-octyl acrylate.
  • the backbones of the graft copolymer may include other types of elastomeric chains.
  • the elastomeric chain may be selected so that the graft copolymer has a transition glass temperature (T g ) below room temperature.
  • T g transition glass temperature
  • the elastomeric chain may have PLA blocks or graft PLA groups.
  • elastomers with pendant hydroxy groups may be conveniently used to form PLA graft polymers.
  • poly(isoprene) (PI) may be used as an elastomeric backbone.
  • polybutadiene or ethylene propylene diene monomer (M- class) (EPDM) rubber may be used.
  • the double bonds in these elastomers can be functionalized, such as by hydrogenation, to saturated hydrocarbon blocks, which can be conveniently utilized to compatiblizing PLA with, e.g. polyolefins.
  • the specific elastomers to be used in a particular embodiment may be selected based on various factors of interest in the particular application, and can be determined by those skilled in the art based on known properties of different elastomeric materials, such as elasticity, mechanical strength, reactivity, solubility, chemical resistance to certain materials, compatibility with other polymers, or the like.
  • the side chains of the graft copolymer may be grafted to the backbone of the graft copolymer through a suitable acrylate group such as a hydroxy- or amine-functionalized acrylate group.
  • a hydroxy- or amine-functionalized acrylate suitable for use as a ring opening polymerization initiator may be used.
  • Suitable hydroxy-functionalized acrylates may include hydroxyethyl acrylate, such as 2-hydroxyethyl acrylate, or 2-hydroxyethyl methacrylate.
  • the initiator and the corresponding lactide or polylactide may be dissolved in a suitable organic solvent, such as anhydrous toluene or
  • tetrahydrofuran Various suitable Lewis acid metal complexes may be used as catalysts for the ring opening polymerization of lactide.
  • tin(ll) octoate also referred to as stannous octoate
  • aluminum isopropoxide may be used.
  • the solution may contain about 1 wt% of stannous octoate based on the total weight of the lactide and the initiator.
  • the solution may be heated to a suitable temperature, such as about 70 °C, and continuously stirred. After the acrylate-terminated PLA is formed, the solvent and other components may be removed, such as by evaporation. The residue may be purified and dried according to standard procedures known to those skilled in the art.
  • the graft copolymer may have a relatively low glass transition temperature (T g ), such as below about 0 °C.
  • the elastomer in the backbone may also have a relatively high melting temperature (T m ).
  • the polyacrylate may include poly(alkyl acrylate), and may be formed from an acrylate monomer such as n-butyl acrylate, n-hexyl acrylate, or n-octyl acrylate, or a combination thereof.
  • the graft copolymer in the composition may be about 1 to about 20 wt% based on total weight of the composition, such as from about 2 to about 10 wt%.
  • the thermoplastic polymer (or PLA) may have a number average molecular weight (Mn) of about 20,000 to about 500,000.
  • the number of repeating units (n) in the PLA may be from 100 to 5000.
  • the Mn for the backbone in the graft copolymer may be from about 50,000 to about 500,000.
  • the Mn of the side chains in the copolymer may be from about 2,000 to about 50,000. All values of Mn listed herein are given in units of g/mol. [0030] . Due to the thermoplastic chains, the composition is also
  • thermoplastic Due to the presence of the graft copolymer and PLA
  • the brittleness of the composition is reduced as compared to a pure PLLA or PDLA polymer.
  • the brittleness of different polymers may be assessed based on the measured-per ⁇ ntages ⁇ f-elongation-at ⁇ ⁇ ⁇ break-in-tensile-tests ⁇ Tensile-test is a-well— established technique known to those skilled in the art, and may be performed according to the ASTM D638 testing standard.
  • the percentage of elongation at break for the composition may be increased from that of pure PLLA by about 5 to about 8 times at room temperature, corresponding to a substantial reduction in brittleness.
  • an exemplary embodiment of the composition may have a percentage of elongation at break of higher than about 7%.
  • the composition may have a percentage of elongation at break of higher than about 10%. In a further exemplary embodiment, the composition may have a percentage of elongation at break of higher than about 20%. In another exemplary embodiment, the composition may have a percentage of elongation at break of about 23% to about 30%.
  • the composition may be prepared by melting a first precursor for the thermoplastic polymer, melting a second precursor for the graft copolymer, and mixing the melt precursors in a mixture at a temperature above the melting temperatures of the thermoplastic polymer and graft copolymer to allow formation of stereocomplexes of lactic acid.
  • the elastomer may be poly(n-butyl acrylate) (PBA) formed from n-butyl acrylate (n-BA) monomers.
  • the mixing temperature for mixing the blend of PLLA and PBA may be about 180 °C or higher, as the melting temperatures of PLLA and PBA-g-PDLA are typically 173-178 °C and 166-167 °C, respectively.
  • the blend mixture of the thermoplastic polymer and graft copolymer may be stirred or otherwise agitated. The mixture may be heated and stirred for a sufficient period of time to allow formation of PLA stereocomplexes.
  • the graft copolymer may be produced in any suitable manner.
  • PAA poly(acrylate acid)
  • the alkyl acrylate and the corresponding acrylate-terminated (capped) PLA may be dissolved in a solution that contains a suitable solvent and a suitable polymerization initiator.
  • the solvent may be dioxane. In a different embodiment, another solvent may also be used.
  • the initiator may be benzoyl peroxide.
  • the solution may be bubbled with an inert gas for a period of time, such as 30 minutes, to remove air, and then heated and stirred to accelerate the desired reaction.
  • the acrylate-terminated PLAs may be formed by reacting a hydroxy- or amine-functionalized acrylate with L-lactide (or poly(L-lactide)), or D-lactide (or poly(D-lactide)), respectively.
  • Hydroxy- or amine-functionalized acrylate suitable for use as a ring opening polymerization initiator may be used.
  • Suitable hydroxy- functionalized acrylates may include hydroxyethyl acrylate, such as 2-hydroxyethyl acrylate, or 2-hydroxyethyl methacrylate. In different embodiments, another suitable initiator may be used.
  • the initiator and the corresponding lactide or polylactide may be dissolved in a suitable organic solvent, such as anhydrous toluene.
  • a suitable Lewis acidic metal complexes such as Sn(Oct)2 (stannous octoate or stannous octanoate), may be added to the solution.
  • the solution may contain about 1 wt% of stannous octoate based on the total weight of the lactide and the initiator.
  • the solution may be heated to a suitable temperature, such as about 70°C, and continuously stirred. After the acrylate-terminated PLA is formed, the solvent and other components may be removed, such as by evaporation.
  • FIG. 1 A specific exemplary synthesis route is illustrated in FIG. 1 and discussed in the Examples.
  • PLA is grafted on the copolymer in a process known as "grafting-through".
  • the values of "n", "x" and “y” may vary depending on the weight percentages, molecular weights, or ratios of the various ingredients added in the reaction process including monomers, PLA macromers, and initiators.
  • the value of "n” may be controlled by adjusting the ratio of initiator and lactide in the reaction mixture.
  • the amounfof the PLA macromer in the resulting copolymer may vary from about 10 to about 50 wt%, such as from about 20 to about 30 wt%.
  • the molecular weight of the PLA macromer may vary from about 2,000 to about 10,000 g/mol, such as from about 5,000 to about 20,000 g/mol.
  • the molecular weight (such as number or weight average molecular weight) of any intermediate or product may be measured using any suitable technique.
  • the molecular weight may be determined using high pressure liquid chromatography (HPLC), gel permeation chromatography (GPC), viscometry, vapor pressure osmometry or beam scattering techniques, among others.
  • graft copolymers such as PBA-g-PLLA and PBA-g-PDLA, may be prepared using a "grafting-from" polymerization technique.
  • a PLA graft copolymer may be formed by providing a copolymer precursor, and reacting a lactic acid with the copolymer precursor to graft a side chain comprising an acrylate-terminated polylactic acid from the copolymer precursor.
  • FIG. 2 An exemplary "grafting-from" synthesis route is illustrated in FIG. 2 for grafting poly(n-butyl acrylate)-b-poly(2-hydroxyethyl acrylate) (PBA-b-PHEA) with PLA.
  • PBA-b-PHEA poly(n-butyl acrylate)-b-poly(2-hydroxyethyl acrylate)
  • PLA poly(n-butyl acrylate)-b-poly(2-hydroxyethyl acrylate)
  • a copolymer precursor, PBA-b- PHEA may be prepared by free radical polymerization using benzoyl peroxide (Bz 2 0 2 ) as the initiator.
  • Bz 2 0 2 benzoyl peroxide
  • PBA-b-PHEA may be grafted with PLA by a "grafting-from” technique using hydroxylated precursors of the n-butyl acrylate polymer as a macroinitiator of the ring-opening polymerization of lactide.
  • a difference between the "grafting-from” technique and “grafting- through” using a PLA macromer is that with the "grafting-from” technique as illustrated in FIG. 2, more densely grafted copolymers may be obtained.
  • LA stereocomplexes may be formed by blending PLA enantiomers by solution casting, or by melt blending. Both solution casting and melt blending
  • melt blending may be conducted for example at 180 °C for about 10 minutes.
  • the melt blend may be a 50:50 blend. That is the polymer containing PLLA and the po ymer containing PDLA in the blend may have a 1 :1 weight ratio.
  • the melt blend may be dried and compression molded at, for example, about 200 °C. Conveniently, the dried blend may have a melting temperature as high as about 220 °C, and a transition glass temperature of about -26 °C.
  • exemplary embodiments disclosed herein may be conveniently used in many applications of different fields.
  • exemplary compositions disclosed herein may be used as thermoplastics or rubber replacements.
  • Rubbers or other thermoplastic materials may be toughened according to exemplary embodiments disclosed herein.
  • thermoplastic material that includes a polymer formed of a first enantiomer of lactic acid
  • the thermoplastic material may be melted and mixed with a melted graft copolymer described herein in which a side chain grafted to the backbone of the graft copolymer includes a second enantiomer of lactic acid, with a chiral configuration opposite to that of the first enantiomer.
  • the melted initial thermoplastic material and graft copolymer may be mixed for a sufficient time to allow the first and second enantiomers of lactic acid to form stereocomplexes, thus linking the polymer in the initial thermoplastic material to the graft copolymer, to form a resulting thermoplastic material.
  • thermoplastic material After the resulting thermoplastic material is solidified, it is less brittle than the initial thermoplastic material.
  • a specific monomer such as L-lactic acid or D-lactic acid
  • the polymers are not necessarily entirely formed of the specified monomer.
  • a PLLA may not be formed of 100% LLA monomer units and a PDLA may not be formed of 100% DLA monomer units.
  • a 100% pure polymer form is difficult to obtain, and the polymers may contain other components such as other monomers and defects.
  • a PLLA polymer may contain a small percentage of DLA or PDLA, and a PDLA polymer may contain a small percentage of LLA or PLLA.
  • the purity of the polymer, including the optical purity of the polymer may be from about 90% to about 100%. In some embodiments, the purity of the polymer may be from about 95% to about 100%. In some embodiments, the purity of the polymer may be from about 85% to about 100%. In some embodiments, the optical purity of the polymer may be above 66%, or above 72%. In some embodiments, the mole fraction of the minor enantiomer in the polymer may be less than 0.14, or less than 0.17.
  • Lactide used in these examples was purchased from Purac
  • InstronTM 5569 table universal testing machine was used to measure stress/strain of the samples according to ASTM D638.
  • Sample PLLA macromers were prepared following the synthesis route (1 ) shown in FIG. 1. For each sample, a selected amount of L-lactide and stannous octoate (1 wt% of the total weight of lactide and the initiator) were dissolved in 150 ml anhydrous toluene in a Schlenk flask under an argon atmosphere. A selected amount of 2-hydroxyethyl acrylate was added to the solution as the ring opening initiator. The amounts of the initiator and the catalyst were adjusted to form different samples with different molecular weights. The resulting mixture was heated to 70 °C and stirred for 3 days. Toluene was then removed under reduced pressure using a rotary evaporator. The residue was purified by dissolution in CH 2 CI 2 and precipitation from the solution by addition of methanol. The precipitate was dried under vacuum at 55-60 °C for 24 hours.
  • Sample IA and Sample IB Two other samples, referred to as Sample IA and Sample IB, were formed with 14.4 g L-lactide and different amounts of initiator and catalyst.
  • Example I was followed but the L-lactide was replaced with D-lactide to produce PDLA macromer samples.
  • Samples HA and IIB 14.4 g of D-lactide was used and the amounts of the initiator and catalyst were adjusted to produce sample macromers with different molecular weights.
  • Example III Synthesis of graft copolymer PBA-g-PLLA
  • PBA-g-PLLA samples were prepared following the synthesis route (2) shown in FIG. 1.
  • 9 g of n-Butyl acrylate (n-BA), 3 g of PLLA of Sample I, and 120 mg (1 wt%) of benzoyl peroxide were dissolved in 25 ml dioxane in a 100 ml Schlenk flask.
  • the resulting solution was bubbled with argon for about 30 min to remove air and then heated to 70 °C with stirring overnight.
  • the hot solution was poured into methanol to precipitate the graft copolymer.
  • Samples IMA and IIIB were also prepared following the above procedure, but with Samples IA and IB as the respective PLLA macromer.
  • Sample NIC was prepared as follows. 5 g of n-Butyl acrylate (n-BA),
  • Example IV Synthesis of graft copolymer PBA-g-PDLA
  • Sample IVC was prepared as follows. 5 g of n-Butyl acrylate (n-BA),
  • Example V Blend of PLLA and PBA-g-PDLA
  • Samples VA and VB (also collectively referred to as Samples V) were prepared with Sample IVA or Sample IVB respectively.
  • Example VI Blend of PLLA and PBA-g-PLLA (Comparison Samples)
  • Samples VIA and VIB (also collectively referred to as Samples VI) were prepared according to the procedures described in Example V, but replacing Sample IVA or IVB with Sample MIA or 11 IB, respectively.
  • test specimens were dried under vacuum, placed in a steel mold (100 mm x 100 mm, sample holding area), and pressed using a CarverTM hydraulic press at 195 °C for 5 min. The press plates and the mold were cooled to room temperature before the press plates were removed from the mold. Dumbbell-shaped specimens of Samples V were punched with a hollow die (die type: ASTM D638 type V) from hot compression-molded plates. For tensile tests, tensile bars of the samples were die-cut from sample materials in plate form.
  • Shaped PLLA (Nature WorksTM, 3051 D) samples, Samples V, and
  • Samples VI were subjected to stress-strain tests at room temperature respectively. Representative measured results are summarized in Table I.
  • the values of "Strain at break" in Table i reflect the tensile strain on a given sample when it broke under stress.
  • Example VIII Synthesis of graft copolymers by alternative routes
  • Sample graft copolymers PBA-g-PLA were also prepared following the synthesis route shown in FIG. 2.
  • poly(n-butyl acrylate)-b-poly(2- hydroxyethyl acrylate) (PBA-b-PHEA) grafted with PLA was prepared.
  • PBA-b-PHEA was prepared by free radical polymerization using benzoyl peroxide (BZ2O2) as the initiator. It was then grafted with PLA by a "grafting from” technique using hydroxylated precursors of the n-butyl acrylate (n-BA) polymer as a macroinitiator of the ring-opening polymerization of lactide as shown in route (2') of FIG. 2.
  • Samples VIII-2 and Vlll-D were also prepared, following the above procedures for forming Samples VIII-1 and Vlll-L respectively, with the exception that, instead of L-lactide, D-lactide was used for forming Samples VIII-2 and Vlll-D.
  • thermoplastic PLA polymers can be conveniently toughened in a relatively simple process by blending melts of PLA of one enantiomer and a graft copolymer of an elastomer and a PLA of the opposite enantiomer. It is expected that PLA stereocomplexes formed in the resulting composition can link the thermoplastic chains to the elastomeric chains, thus reducing the brittleness of the resulting composition as compared to a pure PLA polymer.

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Abstract

La présente invention a pour objet de réduire le caractère cassant d'un matériau thermoplastique contenant un acide polylactique, en faisant fondre et en mélangeant ledit matériau thermoplastique et un copolymère greffé afin de lier le copolymère greffé au polymère thermoplastique, de façon à former un nouveau matériau thermoplastique moins cassant. Le copolymère greffé comprend une chaîne principale élastomère et une chaîne latérale greffée sur la chaîne principale. La chaîne latérale comporte un énantiomère de l'acide lactique contraire à l'énantiomère sur le matériau thermoplastique. L'invention concerne une composition comprenant un polymère thermoplastique et le copolymère greffé, ledit copolymère greffé étant lié au polymère thermoplastique via les énantiomères. L'invention concerne aussi un procédé de formation de la composition, pouvant impliquer de faire fondre des précurseurs du polymère thermoplastique et du copolymère greffé, puis de mélanger ces précurseurs pour permettre aux acides lactiques de lier le copolymère greffé au polymère thermoplastique.
EP11769186A 2010-04-14 2011-04-14 Composition thermoplastique formée à partir d'acide polylactique et d'un copolymère greffé élastomère Withdrawn EP2558518A1 (fr)

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EP11769187A Withdrawn EP2558519A1 (fr) 2010-04-14 2011-04-14 Élastomères réticulés par de l'acide polylactique

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WO2011129772A1 (fr) 2011-10-20
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US20130030128A1 (en) 2013-01-31

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